Hybrid diamond/graphite films: Morphological evolution, microstructure and tribological properties

Diamond films were deposited on silicon substrate by microwave plasma enhanced chemical vapor deposition (MPCVD) using H-2 and CH4 gas mixture. The morphological evolution process was characterized systematically by means of field-emission scanning electron microscopy (SEM), X-ray diffraction (XRD) and Raman spectroscopy. Special attention has been paid to the influence of the methane concentrations on the microstructures of diamond films, which shows a gradual transition from nanocrystalline to microcrystalline films, and finally displays a hybrid diamond-graphite nanostructure with the length of a few micrometers. Finally, the friction behaviour of the hybrid films was studied. The value of the friction coefficient of the hybrid films is 0.10 and the corresponding wear resistance is below 1.9 x 10(-7) mm(3)/N.m in diamond composites/Al2O3 sliding system in ambient atmosphere under dry sliding conditions. It is a convenient path to synthesize hybrid diamond/graphite nanostructures by MPCVD depending on higher methane concentrations in the absence of nitrogen or argon. The structure is appropriate for the potential applications as high efficient mechanical tools. (C) 2016 Elsevier B.V. All rights reserved.